I don't remember enough of class to tell you the right terminology, but in short, it sounds like a cyst. No worries, as long as it isn't growing or getting infected, it is harmless. Even though it popped, it may come back. A typical cyst forms a sac around the pus, the sac is connected to the surrounding tissue pretty strongly. Very likely it will fill up again. Popping it is generally okay, if it raises to the surface (and is poppable) that is exactly what your body is trying to do with it.
Warm compresses may help bring it to the surface and also help rebsorb some of the tissue. If it keeps coming back, or starts to look angry, you may want to get it checked out and removed. It is a simple procedure, the worst part about it would be the lidocaine shot. A few slices, a week or two of antibiotics, you will be good to go.
Do not try lancing it yourself. While this may drain the fluid (if it is more liquid than solid; usually it is thick like cottage cheese and doesn't flow well), it also introduces a chance for infection. Peircing it won't do anything for the sac either, so it is only a temporay fix.
A side story, while we are being gross. A few months back, I removed one from a patient. My doc was over my shoulder walking me through it. He described it as a cheesy substance with that spoiled lasagna smell. To make it worse, as I pulled out the sac, it had chunks of blood and pus on it. They served lasagna that night for dinner, and I just couldn't eat it.